Atmospheric control means



Nov. 4, 1947. J. FQSCHRUMN I 2,439,191

' ATMOSPHERIC CONTROL MEANS v Filed. Sept. 10, 1943 2 Sheets-Sheet 1Nov. 1947. I J. F} SCHRUMN 2,430,191

ATMOSPHERIC CONTROL MEANS Filed Sept, 10, 1945 2 Sheets-Sheet 2 j no.

w I l ,5 llll r Patented Nov. 4, 1947 UNITED STATES PATENT OFFICIE ATMOSPHERIC' CONTROL MEANS Application September 10, 1943, Serial No.501,753

6 Claims. (Cl. 263-8) This invention relates to atmospheric controlmeans, and with regard to certain more specificfeatures to such meansfor reaction or treating chambers including furnaces, lehrs and thelike.

Among the several objects of the invention may be noted the provision ofan atmospheric control for furnaces and other reaction chambers whichallows articlesto be introduced and removed from said apparatus withoutupsetting the desired atmospheric control; the provision of apparatus ofthe class described which positively maintains atmospheric control inrespect to articles passing through the treating chamber throughouttheir entire traverse; the provision of apparatus of this class whichaccomplishes the end with a substantial saving inthe materials whichprovide the controlling atmosphere; and the provision of ap- Daratus ofthe class described which is effective in drafty locations-of thefurnace entrance or exit. Other objects will be in part obvious and inpart pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofthe application of which will be indicated in the following claims.

In the accompanying drawings, in which is illustrated one ofvariouspossible embodiments of the invention,

Fig- 1 is a plan view of the invention;

Fig. 2 is a side elevation drawn to the same scale as Fig. 1;

Fig. 3 is a horizontal section taken on line 3-3 of Fig. 2, but on anenlarged scale;

Fig. 4 is a vertical section taken. on line 4-4 of Fig. 3. being on saidenlarged scale;

Fig. 5 is a diagrammatic longitudinal sectional view on a reduced scaleillustrating a modification and certain principles of operation of theinvention;

Fig. 6 is a diagrammatic vertical section viewed from the left of Fig. 5and illustrating certain operating characteristics;

Fig. 7 is. a view similar to Fig. 6 illustrating certain operatingcharacteristics of certain prior art, and,

Fig.8 is a side elevation illustrating the centralpart of a treatingchamber of this invention.

Similar reference characters indicate corresponding partsthroughout theseveral views of the drawings.

An atmospheric heat-treating furnace, which furnishes an example of oneapplication of the invention, is one: inwhich articles are either placedin, or passed through, the furnace and electrically or otherwise heatedin the presence of a blanketing mass of a reducing (non-oxidizing)atmosphere (gas). Thepurpose of this is to bring the articles up to adesired heat-treating temperature and at the same time to avoidoxidation such as would occur if the articles were heated in anatmosphere of oxidizing gas such as air. Generally (and such an exampleis used herein) the articles aresent through the furnace on acontinuously endless belt. This, of course, implies the necessityfor aninlet and an outlet to the furnace for introducing and removing thearticles. The reducing gas, such as for example partially burned fuelgas, isintroduced in substantial volume at some mid-point of the furnaceand allowed to run out at the inlet and outlet. At the inlet and outletit is generally collected by some type of offtake, burned and disposedof to the outside atmosphere.

t has always been the purpose completely to muffle the articles in thereducing gaseous atmosphere as long as they are at an oxidizingtemperature, and, usually forsome time therebefore and thereafter.

A prior difficulty wasthat the hot-gas, in escaping fromthefurnaceinlets or outlets, tended to rise from the bottom of the furnace.Oxidizing air took itsplace and-crept back into the furnace inlet oroutlet (as the case may be) with a flamecurtain playing from below andarising into the upward offtake. Through thi flame curtain the articlespassed in entering and leaving the furnace, but it was found that thepassing articles themselves blocked off the flame curtain, leavingopenings through which the oxidizing air could enter andcreep back intothe furnace to cause oxidation. The gassupply to the curtain was alsowasteful. All this'will be further elucidated later, in connection withthe drawings. Furthermore, none of the prior solutions adequatelyprevents the unstable conditions that al-' ways occur at an entrance orexit under drafty, variable-pressure, orsimilar surrounding conditions.

To minimize ndii Referring now more particularly to the drawings, thereis indicated at numeral l the muffle part of the furnace built upon asupport 3 and through which passes an open-mesh belt 5. This beltsupports the articles to be carried through th furnace. It is to beunderstood that the muffle compartment of the furnace I is provided withsuitable electricor other heating means and also with a suitable inlet 6(Fig. 8) for the muffling or the reducing gas which is to form thernuiiiing ambient reducing atmosphere for the articles which are passingthrough on the belt 5. The heating elements, being known, are thereforenot shown.

At numeral 1 is indicated the entrance portion of the furnace and at 9the outlet or exit portion. From these extend outside tunnel-like hoodsH, carrying interior spaced fins [3. These interiorly finned hoodssubstantially guard the entrance 1 and exit 9 from the effect of ambientatmospheric draft and pressure disturbances, so that the effects desiredat the entrance I and exit 9 are not substantially disturbed. The fins I3 have the effect of bringing about turbulence in any air that tends toenter through the tunnels and to destroy its entering motion infriction. That is, it breaks up streamline progress of air. toward thefurnace opening. In addition, the tunnel itself forms a cover for theopening guarding it from the direct influence of outside cross currents.

It must be understood that, although the baffled entry guard tunnels llform a part of the invention alone, or in combination with th partssubsequently to be described, nevertheles these bafiied tunnels may beeliminated and the features to be described hereinafter will still beoperative on their own merits. These important features are as follows:

Just beneath the entrance I, also beneath the outlet 9, and below themoving belt are arranged laterally elongate gas oiftake slits 15communicating downwardly with crosswise manifolds ll. These manifolds L1in turn communicate with vertical fiues l9 controlled by dampers 2!.These flues rise to form stacks providing an induced draft, or they maypass to suitable suction apparatus for maintaining the desired draft.The important point is that the muflie gases from the furnace are drawndownward from their naturally elevated positions at the inlet andoutlet, then through the belt 5 and down through the openings [5.

As indicated in Figs. 3 and 4, each opening 15 substantially spans theWire belt 5. Small pilotlight gas nozzles 23 just outside of the slitsl5 serve to keep the descending cascading mass of mufile gas ignited. Itwill be appreciated that ignition does not proceed back into the furnacel, for lack of oxygen therein. Oxygen required for igniting thedescending gas at the slits i5 is pro-' vided by outside air enteringthe tunnels ll, This air creeps in gradually without undue disturbancein view of the bafiles l3. It will b understood that the same ignitingeffect is obtained from the outside air when the tunnels II aredispensed with, as is possible under quiet ambient atmosphericconditions.

In Figs. 5 and 6 is diagrammatically shown the entrance end of analternative without the tunnels H, wherein like numerals designate likeparts.

Operation is as follows:

The furnace I is heated and the reducing gas is introduced therein inquantity enough to displace the air therein and to flow towards itsends. This gas tends to rise. The induced draft effect through themanifold l1 and the flue [9 causes said gas to descend at the inlet 1and outlet 9 to cascade down into the inlet slits l5, thus presenting adownwardly flowing curtain of gas. The outer surface of this downwardlyflowing gas is ignited from the pilot burners 23, combustion beingsupported by adjacent outside air. The flame curtaining effect isdiagrammatically indicated in Figs. 5 and 6 (Fig. 6 is a left-end viewof Fig. 5) wherein it will be seen that no opening occurs through thecurtain for entry of air a even as articles A pass.

In Fig. 7 is shown a diagram corresponding to Fig. 6 but representingthe prior art. It shows what occurs with a rising flame curtain asheretofore used with a flue outlet 0 at the top of the furnace inlet oroutlet and a rising flame curtain from a burner slot at the bottom. Inthis case, open regions 25 occur around passing articles A through whichoutside air proceeds back into the furnace. In addition, if asubstantially large gas flow is not maintained, the gas, as it proceedsoutward, lifts from the conveyor 5. This is due to its heated conditionwhich makes it light. The spaces 25 afford passage for air into thespecified space beneath the gas. It will be noted from Fig. 6 that thepassages 25 are eliminated and from Fig. 5, that behind the curtainthere can be no oxidizing air. It is all positively blocked off,

The invention not only completely blocks off all entry of air into thefurnace and thus eliminates any possibility of oxidation of heatedproducts therein, but also effects a substantial saving in the gas used.This is because, as indicated above, under the old condition air entrycould be somewhat minimized by increasing the rate of gas flow so as tocause a greater sweeping action toward the inlet and outlet of thfurnace. Since minimization of air entry was a desired end, this wasteofgas was resorted to. The present invention avoids it and only enough gasis used to maintain article coverage without the necessity for an excessto maintain the old higher pressure needed at the inlet and outlet.

The purpose of the damper controls 2| is to accommodate the draft tovarious conditions. For example, more draft is required in the offtakeat the front I of the furnace than at the rear 9, because the furnace isgenerally operated hotter at this end. This requires more suction drafteffect to draw down the resulting lighter gases as they tend to emergeat the top of the furnace inlet.

-In Figs. 5 and 6 a sliding control door D is. used which may beadjusted to minimize the outlet or inlet area according to the size ofthe passing articles. It is to be understood that such doors may beapplied at the inlet and out-- let 1 and 9 of Figs. 1-4. Such doors areold and the invention is operable independently of them.

It is to be understood that the invention is applicable to heatednormalizing lehrs, as well as to furnaces per se, where such lehrs areused in association with an interior reducing atmosphere. It is alsoapplicable to box-type furnaces and non-heated gas-treating compartmentsin general.

It is also to be understood that the elements of the invention areindependently applicable to furnace inlets or outlets.

The term special atmosphere is used herein with the meaning oftenattributed to it in the art, namely, a gaseous atmosphere or vapor atsonous non-combustible gases which would require no ignition of thedescending curtain part at the opening 15. It would also include gasesused in other treating compartments, such as for gasing fruits where thepresent principles of producing a descending gas curtain are applicable.

Reference under rule 43 is made to applicants copending applicationentitled Process for atmospheric control, Serial No, 762,047, filed July19, 1947, as a division of this application.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. In apparatus of the class described, a tunnel having an opening, saidtunnel having therein a special atmosphere approaching the opening andnormally tending to rise, a downwardly located moving support movingwith respect to the tunnel and through said opening and carrying alongthe bottom of the tunnel articles to be treated, a manifold providing anextended inlet adjacent and spanning said opening and below the path ofthe support, means for drawing said atmosphere down into said manifoldand through said inlet, and means for igniting said atmosphere as itdescends.

2. An atmospheric furnace having an opening and an article-supportingbelt moving through said opening, a suction box having an inlet locatedbeneath said belt, said inlet being crosswise of said opening andextending substantially across said belt, means for producing asubatmospheric pressure in said box to draw into said inlet atmospherefrom the furnace, and a draft guard constituting a tunnel projectingbeyond said opening and over said belt.

3. An atmospheric furnace having an opening and an article-supportingbelt moving through said opening, a suction box having an inlet 1ocatedbeneath said belt crosswise of said opening, means for producing asubatmospheric pressure in said box to draw into said inlet atmospherefrom the furnace, a draft guard constituting a tunnel projecting beyondsaid opening and over said belt, and spaced interior fins on said guard.

4. An atmospheric furnace having an opening and a reticulatedarticle-supporting belt moving through said opening, and a draft guardconstituting a tunnel projecting from said opening and over said belt,said tunnel having spaced interior fins.

5. In apparatus of the class described, a chamber having an opening forpassage of articles therethrough, said chamber having a flow of acombustible atmosphere therein which tends to rise, a manifold providingan inlet located at the lower side of said opening, and means fordrawing said atmosphere across said opening and downward into said inletto form a downward cascading movement of the atmosphere at the opening,and means to ignite said atmosphere adjacent the outside of the openingto form a flame curtain.

6. In apparatus of the class described, an elongate, open-ended treatingchamber, a reticulated conveyor adapted for travel along the bottom ofsaid chamber for carrying articles to be treated therethrough, saidchamber having an inlet for a special treating atmosphere whichnormally,

tends to rise and an offtake for said atmosphere adjacent each end ofthe chamber below the path of said conveyor, each offtake comprising aslit extending transversely of the chamber for substantially the fullwidth of its open ends, and means for drawing off said atmospherethrough said slits thereby to provide a downwardly flowing curtain ofsaid atmosphere across both open ends of the chamber to exclude theoutside atmosphere therefrom.

JEWETT F. SCI-IRUMN.

\ REFERENCES CITED The following references are of record in the file ofthis patent:

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